Imaging processes performed by Magnetic Resonance Imaging apparatus (hereinafter, “MRI apparatus”) use methods by which the inside of an examined subject is shown in an image while utilizing nuclear magnetic resonance phenomena. More specifically, to cause a nuclear magnetic resonance phenomenon, an MRI apparatus applies a radio-frequency pulse (hereinafter, an “RF pulse”) corresponding to a resonance frequency to a transmission coil, so that the transmission coil generates a radio-frequency magnetic field (hereinafter, an “RF (B1) magnetic field”).
In this situation, because the resonance frequency is proportional to the strength of a magnetostatic field, a relationship is observed where, when the strength of the magnetostatic field becomes higher, the resonance frequency also becomes higher; however, for example, when the magnetostatic field strength exceeds 1.5 tesla (T), the distribution of RF (B1) magnetic fields becomes inhomogeneous due to electrical losses and dielectric resonances occurring on the inside of the subject. In other words, the RF (B1) strength levels become inhomogeneous on the inside of the subject, and the homogeneity of the image also becomes lower. More specifically, partial lowering of the signals and/or lowering of the contrast are observed in the image, which result in degradations of the image. To cope with this situation, for MRI apparatuses of which the magnetostatic field strength exceeds 1.5 T, for example, methods have conventionally been proposed for making the RF (B1) strength levels homogenous.
Even with the conventional techniques, however, it is still difficult to make the RF (B1) strength levels completely homogenous, and the problem of inhomogeneity of the RF (B1) strength levels still remains. Thus, the problem of the degradations of the image caused by the inhomogeneity of the RF (B1) strength levels also still remains. To cope with this situation, there is a demand for a technique that is able to reduce degradations of the image caused by the inhomogeneity of the RF (B1) strength levels.